I always think of things like letting someone who appears to be in greater need go in front, as an act of courtesy. Of course courtesy is a huge component of class, but to me, there is something else going on where 'class' is concerned. It's 'quiet'. It's almost undetectable, undefinable.....and yet you always recognize it when you're in the presence of it.
I think the fact that someone who may in fact be in a 'higher class' than those around them, but have a soft way of making it appear that there is no difference.....is class.
Someone mentioned the Royals and Princess Diana. I always thought it was classy when she would get right down on her haunches when she spoke to children. She didn't speak down to them from the position of bending from the waist.....she got right down to their physical level to talk to them.